Inferring origin of mercury inclusions in quartz by multifractal analysis
- 1Geological Survey of Hokkaido, Hokkaido Research Organization, N19 W12, Kita-ku, Sapporo, Hokkaido 060-0819, Japan
- 2Institute for Geothermal Sciences, Graduate School of Science, Kyoto University, Noguchibaru 3088, Beppu, Oita 874-0903, Japan
- 3Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan
- 4Department of Natural Science, Faculty of Education, Shiga University, Hiratsu 2-5-1, Otsu, Shiga 520-0862, Japan
Abstract. In order to refine our understanding of how fluid inclusions were trapped in the host minerals, we non-destructively observed mercury inclusions (liquid Hg0) in quartz samples using X-ray computed tomography (CT) technique. The X-ray CT apparatus can observe internal structures of the samples and give cross-sectional images from the transmission of the X-rays through the samples. From the cross-sectional images, we obtained three-dimensional spatial distributions of mercury inclusions, and quantitatively analyzed them using fractal and multifractal methods. Although the samples were from different geological settings, the resultant fractal dimensions were 1.70 and 1.71 for the San Benito and Itomuka samples, respectively. The fractal dimensions were also close to those predicted by diffusion-limited aggregation models and percolation theory, which are controlled by the irreversible kinetics. Given the fractal dimension and its implied mechanism, we conclude that the mercury-bearing fluids were not primary fluid inclusions, but migrated into the pre-existing cracks of quartz crystals by diffusion processes.